使用android studio(3.5) 呼叫 mySQL stored procedures時出現錯誤(若僅執行單行可正常使用，但多行無法一次執行):

以下為文件內容:

Android studio main_activity.java(部分)

        @Override
        protected String doInBackground(String... strings) {
            try{
                Class.forName("com.mysql.jdbc.Driver");
                Connection con = DriverManager.getConnection(url, user, pass);
                String result ="";
                Statement st = con.createStatement();
                ResultSet rs = st.executeQuery("call login(@fname, '"+account+"', '"+password+"'); select @fname;");

                ResultSetMetaData rsmd = rs.getMetaData();

                while(rs.next()){
                    result += rs.getString("fname").toString()+"您好!";
                }
                res = result;

            }catch (Exception e){
                e.printStackTrace();
                res = e.toString();
            }
            return res;
        }

mySQL stored procedures:

CREATE DEFINER=`currency`@`%` PROCEDURE `login`(out fname varchar(5), in acc varchar(100), in pwd varchar(50))
BEGIN
	Declare exist int;
    select count(*) into exist from client where account = acc and code = pwd;
    if exist = 0 then
		set fname = '遊客';
	else
		select f_name into fname from client where account = acc and code = pwd;
	End IF;

END

補充:
目前已經用以下方法暫時繞過問題了，但各位大大要是有更好的方法也歡迎留言喔!:

CallableStatement cstmt = con.prepareCall("{call login(?,?,?)}");
                    cstmt.registerOutParameter(1, Types.VARCHAR);
                    cstmt.setString(2, account);
                    cstmt.setString(3, password);
                    cstmt.executeUpdate();